swiftUi propertWrapper 自定义标记属性

上篇文章我们知道@Status  的作用了

那么我们也可以自己定义类似的这种标签。。

首先我们先来看下不使用属性标签，向导页面如何写

1//
2//  PropertyWrapperView.swift
3//  learn_swiftUi
4//
5//  Created by liuan on 2020/9/4.
6//  Copyright © 2020 liuan. All rights reserved.
7//
8
9import SwiftUI
10extension UserDefaults{
11    public enum Keys{
12        static let hadSHowUserGuide = "hadSHowUserGuide"
13    }
14    var hasShowUserGuide: Bool{
15        set{
16            set(newValue,forKey: Keys.hadSHowUserGuide)
17        }
18        get{
19            bool(forKey: Keys.hadSHowUserGuide)
20        }
21    }
22}
23struct PropertyWrapperView: View {
24    @State private var showText = UserDefaults.standard.hasShowUserGuide ? "已经展示":"尚未展示"
25    var body: some View {
26        Button(action: {
27            if(!UserDefaults.standard.hasShowUserGuide){
28                UserDefaults.standard.hasShowUserGuide = true
29                self.showText = "已经展示"
30            }
31        }){
32            Text(self.showText)
33        }
34    }
35}
36
37struct PropertyWrapperView_Previews: PreviewProvider {
38    static var previews: some View {
39        PropertyWrapperView()
40    }
41}

第一次进来 现实尚未展示 ，点击后现实已经展示

如果改为标签呢

1//
2//  PropertyWrapperView.swift
3//  learn_swiftUi
4//
5//  Created by liuan on 2020/9/4.
6//  Copyright © 2020 liuan. All rights reserved.
7//
8
9import SwiftUI
10//extension UserDefaults{
11//    public enum Keys{
12//        static let hadSHowUserGuide = "hadSHowUserGuide"
13//    }
14//    var hasShowUserGuide: Bool{
15//        set{
16//            set(newValue,forKey: Keys.hadSHowUserGuide)
17//        }
18//        get{
19//            bool(forKey: Keys.hadSHowUserGuide)
20//        }
21//    }
22
23//}
24@propertyWrapper
25struct UserDefaultsWrappler<T> {
26    var key: String
27    var defaultValue:   T
28    init(_ key:String, defaultValue: T){
29        self.key = key
30        self.defaultValue = defaultValue
31    }
32    var wrappedValue: T {
33        get{
34            return UserDefaults.standard.value(forKey: key)as? T ?? defaultValue
35        }
36        set{
37            UserDefaults.standard.set(newValue, forKey: key)
38        }
39    }}
40
41struct PropertyWrapperView: View {
42    @UserDefaultsWrappler("hadShowUserGudie", defaultValue: false)
43    static var hadSHownUserGudie: Bool
44    
45    @State private var showText = PropertyWrapperView.hadSHownUserGudie ? "已经展示":"尚未展示"
46    var body: some View {
47        Button(action: {
48            if( !PropertyWrapperView.hadSHownUserGudie){
49                 PropertyWrapperView.hadSHownUserGudie = true
50                self.showText = "已经展示"
51            }
52        }){
53            Text(self.showText)
54        }
55    }
56}
57
58struct PropertyWrapperView_Previews: PreviewProvider {
59    static var previews: some View {
60        PropertyWrapperView()
61    }
62}